1. Field of the Invention
The present invention relates generally to air purifiers, and particularly to photocatalytic purifiers.
2. Technical Background
Most fan coil units consist of a water coil or a direct expansion coil, a fan, and ductwork to distribute conditioned air. Before heating or cooling, air is directed through a filter of some sort. There are various types of filters. One type of filter is referred to as a media filter. This type of filter retains dust and other particulate matter. After prolonged usage, media filters become clogged and need to be replaced.
Another type of filter currently being used is known as a HEPA filter. HEPA is an acronym for “high efficiency particulate air.” HEPA filters can capture 99.9% of all particles, including sub-micron sized particles. These filters are useful in mitigating the effects of bioaerosols and dust. They are currently being used in hospitals, manufacturing clean rooms, and in other applications where clean air is considered vital. Typically, HEPA filters have an operational life span of twenty-four (24) months. After that, efficiency decreases markedly, and HEPA filters must be replaced.
Another type of filter currently being used are activated carbon adsorption filters. These filters were developed in response to industrial emissions of volatile organic compounds (VOCs). In an activated carbon adsorption system, contaminated air is directed across a bed of carbon. The carbon extracts the VOCs from the air and adsorbs the VOCs by holding them to its surface. One problem with activated carbon adsorption filters is that the air stream being filtered cannot have a high moisture content because carbon adsorbs moisture. Air having a high moisture content will quickly fill the carbon bed to capacity. Second, the air being filtered cannot include a large amount of particulate matter. The particulate matter will also clog the carbon bed. Thus, the activated carbon adsorption filter may require a pre-filter to reduce the particulate content and a dehumidifier to reduce moisture content to be effective.
An air filter is needed that substantially eliminates odors, VOCs, and bioaerosols from an air mass without requiring extensive service or maintenance. A need exists for a photocatalytic air purifier that can be conveniently installed and removed for maintenance purposes.